In my current ad account, it says 'metric in development' for 'Video Plays'. As per below announcement, this would be rolling out in the coming weeks.

At the moment, 'Unique clicks to play video' is a metric that shows up in Facebook Ads API but I can't seem to get it to populate [in DataStudio]. Tried it with month as a dimension the first time and later with Post Message. Didn't work. Perhaps, this will change quickly.